Curving an edge of a polygonal mesh in blender
Is it possible you've simply got too many polygons at too early a stage to get smooth curvatures easily?

This illustration may not be exactly what you're looking for, but shows the kind of variation you can get from a Bevel modifier and subdivision:




Shows the mesh. A 2-segment  Bevel modifier is assigned, by weight. The weights on various edges are adjusted to increase/decrease the intensity of the crease after subdivision (The lower the weight, the sharper the crease, relative to the base bevel width set in the modifier)
Shows the Bevel modifier applied: what it's actally done
4,5 Show the result after 2x Catmull-Clark Subdivision.


I haven't gone all the way here - you could apply the Bevel, and go in to tweak the topology to remove any residual pinching, etc.